Data terminals such as routers or switches have an interface for local applications, such as for a local area network, which interface is referred to in IEEE Draft Recommendation P802.3z as the 1000BASE-X interface, and which is known in the literature as the Gigabit Ethernet interface. However, this interface has only a very restricted range of a few hundred meters. If one wishes to physically extend local area networks or form MAN or WAN networks, then these Gigabit Ethernet signals must be transported via transmission networks. Normally, in Europe, these transmission networks make use of transmission systems which operate on the basis of the synchronous digital hierarchy SDH in accordance with ITU Recommendation G.707. In the USA, these systems operate on the basis of the SONET Standard, which is likewise defined in G.707.
An object of the present invention is to specify a circuit arrangement and a method in which Ethernet signals can be inserted in SDH/SONET systems.